大型工房内爆炸冲击波流场分布规律

Distribution Law of Flow Field of Shock Wave in Large-scale Workshop

为可靠掌握大型工房结构内爆炸冲击波流场分布特征,对缩尺比例分别为1∶5、1∶7.5和1∶10的工房缩比模型以较小的网格尺寸(空气和炸药均按比例缩小)进行有限元计算。通过计算得出,具有相同单元数量的3个数值模型得到的被爆区相同比例距离处冲击波超压峰值完全一致,其冲量为模型的几何比例系数。进一步分析表明,具有相同网格结构的数值模型计算结果具有相似性,在爆炸冲击波仿真计算中网格绝对尺寸并非计算精度的决定因素。这一现象的发现,指出了提高大型复杂结构中爆炸冲击波计算可靠性的网格划分方法。在此基础上,对一种大型工房内爆炸冲击波的传播规律进行分析,发现冲击波从窗户流入、在被爆区地面及梁底的反射与绕射、不同方向冲击波的碰撞迭加等过程是造成被爆区内冲击波压力多次振荡并持续很长时间的主要原因,而工房内超压峰值较大的区域与冲量较大的区域并不重合,因此在进行工程安全评估时应予以重视。

In order to obtain the reliable calculation results of flow field of shock waves due to an internal explosion in a large-scale workshop structure,a set of 1∶50,1∶7.5 and 1∶10 reduced scale model are firstly tried so as to utilize a smaller grid size in a finite element simulation(both air and explosive are scaled down in the same way).It is found that the peak values of shock wave overpressure calculated at the same proportional distance in the blasted zone are exactly the same for numerical models with the same amount of elements and configuration,and the impulses of such models keep scaled just by the geometric scale factor,indicating that the numerical results from models with the same mesh configuration satisfy the law of similarity,and that the absolute mesh size does not dominate the accuracy in a numerical simulation of explosive shock wave.This observation provides a reliable way in meshing a large-scale workshop for explosive shock wave calculation.On this basis,the propagation of blast wave in a large-scale workshop is studied numerically.The results reveal that the process of shock wave flowing through windows,reflecting and diffracting from ground and bottom of roofs,colliding and superposing from different directions are the main characteristics in the blasted zone,and that such processes induce a long duration and vibrating overpressure whose distribution of peak overpressure and impulse are quite not coincident to each other.This should be taken into consideration in the safety assessment of such workshops.